Double-acting billet extrusion presses



Feb. 26, 1957 E. NORMAN DOUBLE-ACTING BILLET EXTRUSION PRESSES Filed July 8, 1952 IN V EN TOR. f fi/c NORMA /v BY 3644M! MW ATTORNEYS DOUBLE-ACTING BILLET EXTRUSION PRESSES Eric Norman, Bournemouth West, England, assignor to The Loewy Engineering Company Limited, London, England, a corporation of Great Britain Application July 8, 1952, Serial No. 297,651

Claims priority, application Great Britain July 12, 1951 2 Claims. (Cl. 207-9) This invention relates to billet extrusion presses of the double-acting type. In these presses, the billet chamber is open at both its ends and has preferably a bore of uniform diameter throughout, the extrusion tools being radial- -ly disposed with respect to the axis of that chamber. The

presses are equipped with two pressing stems and the necessary hydraulic means for moving them, the pressing stems being so arranged with respect to the container that they can enter the billet chamber from either end. The pressing stems are further adapted to act in opposition on the billet metal in the chamber and to extrude the billet metal from that chamber at an angle to its axis, and thus to that of the press.

The containers of billet extrusion presses are subject to considerable axial forces whilst billets are extruded therefrom, and also at other times, and the present invention is mainly concerned with the problem of supporting the container of such a press against displacement due to any unbalanced axial forces.

In the case of double-acting extrusion presses, the con tainer can be completely or almost completely relieved of any axial forces while extrusion is in progress by the expedient of equalising the pressures which act on the pressing stems during their operative stroke. Nevertheless, it is, in practice, not always possible to keep the container of a double-acting extrusion press free from any axial forces. Such forces may, for instance, occur when, after termination of an extrusion operation, one of the two pressing stems clings so firmly to the residueof the extruded billet that a special effort is required to withdraw that pressing stem from the billet chamber. Ora billet or billet residue to be ejected from the billet chamber has become jammed or wedged therein and requires therefore a special effort to remove it.

It is an object of the invention to provide a double-acting billet extrusion press having improved means for supporting its container against axial displacement.

tates Patent It is a further object of the invention to provide a double-acting billet extrusion press in which the billet container is supported in the press against displacement due to any unbalanced axial forces, in such a manner that the container can be slidingly supported in the press bed.

According to the present invention, a double-acting billet extrusion press is provided at either side of its container unit with balancing means in the form of prossure-loaded hydraulic thrust bearings capable of resisting axial forces to which the container is subjected, the thrust bearings comprising hydraulic rams displaceable in stationary cylinders in a direction parallel to the axis of the press. In this way, the container and its holder are firmly held against any axial displacement, provided that the axial forces acting on the container unit do not exceed the combined pressure load on the thrust bearings at one side of the container. The container holder can, therefore, have a sliding or floating support on the press bed, which is a great advantage.

Any axial forces to which the container is subjected will be directly transmitted from the container unit through 21,782,921 Patented Feb. 25, 1957 the thrust bearings on to a stationary part of the press without causing any heavy loads in the container holder, so that the latter does not need strengthening.

For practical purposes, it will generally be sufficient to make the combined pressure load on the thrust bearings at one side of the container unit sufiiciently large to resist axial forces of the order caused by one of the two above-mentioned contingencies. In exceptional cases, however, it may occur that one of the two pressing stems will exert its full extrusion pressure on the container without being balanced by pressure from the other pressing stern. In such an event, the thrustbearings provided according to the invention will normally not be capable of resisting displacement of .the container unit.

According to a further feature of the invention, safety means are provided which prevent any axial displacement of the container unit due to unbalanced axial forces, the safety means comprising a mechanism which, upon axial displacement of the container unit, actuates a hydraulic valve gear which is effective to reduce the unbalanced pressure to such an extent that the displacement of the container ceases.

In practice, the thrust hearings will be so positioned that a small clearance is left between them and the container unit, and the actuating mechanism for the valve gear will be so set as to become operative only after the container unit has been displaced beyond that clearance. In this way, the container unit can make small and harmless deviations without actuating the safety means.

The hydraulic thrust bearings are preferably mounted on stationary parts ofthe main structure of the press, such as the main hydraulic cylinders provided for the two pressing stems, as these parts are strong enough in themselves to resist the axial forces to which the thrust bearings may become subjected. In most extrusion presses, however, the distance between the main cylinder of the press and its container unit is rather long. The necessity of providing thrust bearings with rams of corresponding length can be avoided by the arrangement of separate distance pieces or spacer members interposed between the rams and the container unit. They may be slidingly supported in the press, for instance, by means of brackets attached to the press columns.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings:

Fig. 1 is an elevation'partly in section, of a double acting billet extrusion press having container-supporting means according to the invention.

.Fig. 2 is a section along the line II--lI of Fig. l.

The press shown inthe drawings has a bed or base frame 10 which, at each end, supports a hydraulic cylinder 11 having a ram 12. The two cylinders have lugs 13 through which columns or tie-rods 14 are passed which are fastened to the lugs. Attached to the rams 12 are pressing stems 15. A container unit, comprising a container proper 16 and a holder 17, is arranged midway between the cylinders 11, the container having a billet chamber 18 which extends from one end of the container to the other and is of uniform diameter throughout. The extrusion toolsof which one only is shown at 19-are arranged radially with respect to the axis of the billet chamber 18 and thus to that of the press. The pressing stems 15 are so arranged with respect to the container 16 that they can enter the billet chamber from either end and act in opposition on the billet metal in the chamber, extruding the billet metal at an angle to the axis of that chamber through one of the tools 19.

Presses of this type are particularly suitable for the extrusion of a continuous sheathing of aluminum or light metal around an electric cable.

The container holder 17 has feet 20 which rest on radial- 1y extending guideways 21 on the base frame 10 (Fig. 2) without being fastened thereto. The container unit 16, 17 is thus slidingly or fioatingly supported in the press.

Arranged in the spaces between the container unit 16, 17 and the cylinder-s 11 are pressure-loaded hydraulic thrust bearings capable of balancing axial forces to which the container unit is subjected. These thrust bearings consist each of a cylinder 22 and a ram 23, the former being mounted on the cylinders 11 and the latter being displaceable in cylinders 22 in a direction parallel to the axis of the press. Interposed between the rams 23 and the container holder 17 are distance pieces or spacer members 24 which are slidingly supported in brackets 25 attached to the press columns 14.

As can be seen from Fig. 2, there are two thrust bearings at either side of the container unit, arranged diametrically opposite each other, whereby eccentric forces on the container unit are avoided.

In practice, the spacer members 24 are so positioned relative to the container holder 17 that a small clearance is left between them and the container holder. By equalizing the pressures which act on the pressing stems 15 during the extrusion of billet chamber 18, the axial forces acting on the container unit 16, 17 during the actual extrusion operation will be balanced, and the container unit will therefore not tend to displace itself on its guideways 21.

Should, however, for any of the above-mentioned reasons, such as the resistance of a pressing stem to withdrawal, or the resistance of a billet or billet residue to ejection, an unbalanced axial force be set up in the container unit 16, 17, the latter will be displaced axially and thereby come into engagement with one set of spacer members 24. The unbalanced axial force will thereby be transmitted to the rams 23 of the hydraulic thrust bearings. If the combined pressure load on these thrust bearings is large enough to resist the unbalanced axial force, then the displacement of the container unit Will cease. For most practical purposes, it will be suflicient to make the combined pressure load on one set of thrust bearings slightly in excess of the return power of the corresponding pressing stems 15 as the unbalanced axial forces normally to be encountered will not be greater than this return power.

However, it may occasionally occur by accident that the container unit 16, 17 is subject to axial unbalanced forces which exceed the combined pressure load of one set of the thrust bearings. In this case, in order to prevent displacement of the container unit and to protect the parts of the press from being over-loaded, suitable hydraulic safety means may be provided which reduce the unbalanced pressure on the pressing stem 15. These safety means comprise a valve gear (not shown here), which is operated as soon as the container unit begins to be displaced beyond the clearance provided between itself and the spacer members 24. Upon operation of the valve gear, the supply of pressure fiuid is cut oil? from the cylinder 11 which is the source of the unbalanced pressure on the container unit. Upon any further displacement of the container unit, the valve gear opens an exhaust valve of this cylinder, so that the pressure in the cylinder will be reduced.

The invention is capable of various other embodiments than the one shown and described here.

What is claimed is:

1. In a billet extrusion press of the double-acting type, a container having a billet chamber open at both ends, two pressing stems adapted to enter the billet chamber at opposite ends, hydraulic means comprising cylinders for moving said pressing stems into the billet chamber, tie rods connecting said main cylinders, a holder for said billet container, means slidingly supporting said holder to permit movement of the billet container and the holder in the direction of movement of said pressing stems, pressure loaded hydraulic thrust bearings at the side of said billet container in alignment with the movement thereof having a predetermined spacing between said thrust bearings and said billet container holder whereby axial displacement of said billet container between said thrust bearings is permitted and displacement beyond said predetermined spacing between said thrust bearings and said billet container holder is prevented by abutment of said billet container holder with said thrust bearings.

2. In a billet extrusion press of the double-acting type, a container having a billet chamber open at both ends, two pressing stems adapted to enter the billet chamber at opposite ends, hydraulic means comprising cylinders for moving said pressing stems into the billet chamber, tie rods connecting said main cylinders, a holder for said billetcontainer, means slidingly supporting said holder to permit movement of the billet container and holder in the direction of movement of the pressing stems, pressure loaded hydraulic thrust bearings at the side of the billet container in alignment with the movement thereof, said thrust bearings including movable distance pieces between said thrust bearings and said billet container holder having a predetermined spacing between said thrust bearings and distance pieces and said billet container holder whereby axial displacement of said billet container between said thrust bearings and distance pieces is permitted and displacement beyond said predetermined spacing between said thrust bearings and distance pieces is prevented by abutment of said billet container holder with said distance pieces.

References Cited in the file of this patent UNITED STATES PATENTS 

